The present invention is directed to the field of organic chemistry in general and specifically to the preparation of pyrroles.
Pyrroles are important heterocycles that occur in porphyrins, pigments and other natural products, have found applications in materials science, and are common components in molecular recognition and self-assembly ensembles. Pyrrole may be synthesized a number of ways, often using classic condensation reactions between activated methylenes and amino ketones. However, these reactions are limited by their inefficiency, functional group incompatibility or the limited variety of substituents that can be introduced around the pyrrole. For example, classic pyrrole syntheses suffer from cross coupling side reactions and work best only with symmetrical pyrroles.
More recent pyrrole syntheses reactions typically utilize specialized methodologies that, themselves, are also limiting. Alternatively, the reactions excel at accessing one substitution motif, but are cannot be used for other substitution motifs. As a result, there is no single strategy for efficiently preparing all combinations of substituted pyrroles from readily available materials. Thus, there is a need for improved synthetic techniques that may be used with materials that are known and easy to handle in order to allow the preparation a large variety of pyrroles. It is also desirable that the new methods be efficient and stereoselective. Importantly, there is a need for synthetic methods that are flexible and that offer access to pyrroles that are difficult to prepare by standard methods.